Need advice on multiple fronts

[CenterRotation]

Budget (including currency): $1500 USD

Country: USA

Games, programs or workloads that it will be used for: Plex NAS

Other details (existing parts lists, whether any peripherals are needed, what you're upgrading from, when you're going to buy, what resolution and refresh rate you want to play at, etc): 

 

So let me make a long story as short as possible.

I am trying to decide on multiple things at once.  Here of the details

 

I live in a house that is approximately 5000 sq feet.  We currently use all streaming services for entertainment (plex, netflix, etc).  We have 6 televisions in the house that are used various amounts for streaming.  I currently use a Google mesh set up for the house. I have attached the network speed test information to this post.  Occasionally when I am streaming to the family room, we get some stuttering or Plex tells me that the internet connection is not able to stream the video file in its original quality. this was annoying.  I decided to have somebody come out and take a look at the house to see what it would take 2 potentially hard wire the network in our home. the estimate was between 6-7,000 dollars. That made me think that there had to be a better option.

 

I thought I could solve the problem if I moved the cable modem to the main family room and built a NAS for plex streaming and then connect it to the home theater directly. Right now I have been running plex off of the main desktop. This is the build I came up with after a lot of reading and video watching. All this NAS will do is handle plex and plex related programs. https://pcpartpicker.com/list/MLgM68 I'll usually only be running 1-2 streams and never more than 5. Thoughts on the legitimacy of that build? Second question, is that build any more powerful than just buying a 6 bay synology? I was planning on running Unraid. I read that Docker would be easier to use with Unraid than synology. 

 

Any kind of guidance would be very appreciated.